This invention relates to a method and apparatus for processing photographic material. In particular, the invention relates to a method of processing which uses a low volume of processing solution.
Conventional processing of photographic material requires the use of large tanks of processing solutions. Each tank contains a processing solution such as developer, bleach, fixing solution or washing solution. The material is transported through each tank in turn. There is a tendency for the solutions to carry over from one tank to another leading to pollution of the solutions. Conventional processing has several other drawbacks. The temperatures which can be utilized are limited and therefore the process is slow. The composition of the solutions must be stable over long time periods in the processing tanks. Replenishment of the solutions is difficult to control. The processing apparatus is also very large due to the number of processing tanks.
To overcome the problems of conventional deep tank processing surface application of the processing chemicals was developed. In previous surface application methods a volume of solution is applied to the surface of the material being processed. However, previous surface application methods have several drawbacks. If the solution applied to the material is just left on the material in a static condition the processing will be very slow and inefficient because there is no agitation and by-products accumulate in the material layers and slow down processing. This method is also prone to non-uniformity of processing.
It is also known to process the material within a rotary tube. The material to be processed is placed emulsion side facing inwards within the tube. Solution is added and the tube rotated. Large volumes of processing solution (70 ml./sq. ft and upwards) will process the material effectively so long as rotation is not so fast as to cause dispersion of the solution puddle. Rapid rotation of the device is however very desirable to quickly and evenly distribute a given small volume of solution over the whole surface of the material so that processing is uniform from one end to the other. If the rotation is too slow there will be seasoning of the small volume of solution by the front end of the material and processing will be different at the back end of the material. Small volumes of processing solution (50 ml./sq. ft or less) do not properly process film or paper because when the device is rotated, even at low speeds of rotation, the solution puddle is dispersed and spread over the whole surface of the material. Consequently there is no agitation. This leads to several processing defects. Processing is streaky, non-uniform and also slow because of local consumption and the accumulation of by-products. There is no surface mixing and chemical economy is therefore low.
The invention aims to provide a method and apparatus in which the above mentioned problems are overcome. The defects can be overcome by using a rotating device in such a way as to provide a means of sweeping the surface of the material to be processed clean of solution at each revolution.
It is an aim of the invention to provide a processor and a method of processing in which only very small volumes of solution are necessary similar to the volumes used to replenish large tank processors but which gives satisfactory results in terms of sensitometry and uniformity.
The invention provides a method in which a single small volume of processing solution for a given process stage is added to a length of material to be processed and which spreads and mixes the whole volume of the solution continuously while processing is occurring.
A given small volume of processing solution is spread repeatedly over the entire length of the material to be processed. The volume used must be in excess of that which is absorbed by the material. The excess volume required need only be small. The method allows surface application of processing solution but also enables mixing and redistribution of seasoning products.
According to the present invention there is provided a method of processing a photographic material, comprising the steps of loading the material into a chamber adapted to hold the material therein, introducing a metered amount of solution into the chamber, rotating the chamber and continuously sweeping the surface of the material as the chamber rotates to thereby form a wave in the solution through which the material passes, the whole volume of solution for a given stage being spread over the whole material area in a repetitive manner to enable uniform processing.
The present invention further provides an apparatus for processing a photographic material, comprising a chamber adapted to hold the material therein, means for introducing a metered amount of solution into the chamber, means for removing the solution from the chamber, means for rotating the chamber and means for sweeping the surface of the material at each rotation of the chamber, thereby to form a wave in the solution through which the material may pass.
The invention further provides a method of processing photographic material comprising the steps of loading the material onto a carrier with the photosensitive side facing outwards, the carrier resting on drivable rollers such that the clearance between the surface of the material and the rollers is minimal, the rollers being located within a container of processing solution, driving the rollers, the rotation of the rollers causing the carrier to rotate and thus the material to pass through the processing solution, thereby providing agitation and mixing of the solution on the surface of the material to enable uniform processing.
The invention yet further provides an apparatus for processing photographic material, comprising a container for holding processing solution, a number of drivable rollers located within the container, and a carrier for carrying the photographic material with the photosensitive side facing outwards, the carrier resting on the rollers, the drivable rollers and the carrier being spaced such that when the carrier is loaded with the material the gap between the surface of the material and the roller is minimal.
The method and processor of the invention allow uniform and rapid processing to be carried out with only very small amounts of processing solution, in the order of 0.5 to 6 ml./linear foot(1.6 to 19.8 ml/linear meter) of 35 mm film and these volumes can be compared with the replenishment rate for a typical 400 speed color negative film in the industry standard Flexicolor C-41 process of about 6 ml/linear foot. The ability to use very low volumes does not preclude the use of larger volumes in the method and apparatus of the invention although it is not necessary to do so. Only a single processing space is required. The appropriate solution for each processing stage is added and removed sequentially from the processing space. Therefore the processing apparatus may be smaller than those of the prior art.
It is also possible to carry out rapid processing in the processor because the volume used is equal to the replenishment volume used in a conventional deep tank processor and is disposed of after the process. Thus solutions which are stable for only a short time can be used for the development, stop, bleach, bleach-fix, fix and wash stages and any other stage. In addition the temperature in the processor can be much higher than in a conventional large tank processor, up to approximately 80xc2x0 C., because the solutions are used within a few minutes and then disposed of This avoids any problems of evaporation and crystallization that can occur with large tank processors at high temperatures. Thus high temperature allows more rapid processing. The usage rate of the solutions is no higher than in large tank processors and in many instances can be less. This is particularly true since in the method of the invention processing solutions can be run close to exhaustion which is not possible in a conventional processor. Thus the method of the invention can provide much lower chemical usage rates than a conventional method. Process cycles can be changed very quickly just by changing the timing of each stage. This allows the process to be xe2x80x9cinstantly customizedxe2x80x9d for a particular film which results in better film performance. For example, the processor recognizes any manufacturer""s film and will adjust the cycle time to the optimum value for that film. This ability cannot be accomplished in a conventional method or apparatus. Different amounts of any solution used in any stage can be added merely by means of software control of the solution delivery system. Temperature can be changed quickly because of the small size of the equipment. The invention can accommodate any process for color film, color paper, reversal film, reversal paper, black and white film or paper.
The method of the invention can also be used for Redox amplification (RX) processing since small volumes of potentially unstable solutions can be used. Thus developer amplifiers, amplifiers or intensifiers and silver bleaches containing hydrogen peroxide or compounds which liberate hydrogen peroxide which can be unstable and not practical to use in conventional methods and apparatuses, can be used simply, easily and reproducibly within the method and apparatus of the invention.
The method of the invention uses component solutions which are kept before their use in containers substantially free of air access and which are stable over long periods of time. Since the solutions used to process film are fresh every time a film is processed, processing consistency is superior to that in a conventional large tank processor. In a conventional large tank processor, variations in processing can occur because it has been idle for some time or because of a low throughput of film. These variations are eliminated by the method and apparatus of the invention.
Since the developer solution is made from two compositions which are stable until mixed and the solution is used within thirty seconds of mixing the developer solution does not need to include anti-oxidants. This eliminates the cost of the anti-oxidants.
Continuous processing machines are replenished in order to make up for chemistry used in processing films. To maintain the chemical levels accurately the replenishment rate must also be accurate. The replenishment rate depends on the film type, that is whether the film is 100, 200, 400 or 800 speed, and also on the utilization of the processor. Since the film type will vary and the utilization will vary the ideal replenishment rate will vary. The replenishment rate is not easy to change to accommodate these factors and in order to monitor the state of the process a special type of film called a control strip is put through the process. A control strip is pre-exposed by the manufacturer under strictly controlled conditions and the correct response from this control strip is measured by the manufacturer in a process that is xe2x80x9con aimxe2x80x9d and supplied with the control strips the process operator will use. The process operator or customer will run a control strip through the process, measure the control strip on a densitometer and compare the result with a correctly processed check control strip supplied by the manufacturer with the pre-exposed control strips. The result of this test will tell the process operator if the replenishment rate is correct or if it needs to be increased or decreased to bring the process xe2x80x9con aimxe2x80x9d. The use of control strips is both costly and time consuming and it is desirable to be able to eliminate the need for their use. This can be achieved by the method of the invention since the processing chemistry is made from stable concentrates just before use and then disposed of immediately after use. The stable concentrates are supplied by the manufacturer and are of the correct composition thus the processing chemistry is xe2x80x9calways freshxe2x80x9d and does not age, season or deteriorate as in conventional processors. Thus control strips are not needed. This eliminates the cost of control strips and also the labor and downtime needed to process the control strips.
In conventional large tank processors low utilization of the processor is a major problem because the standing solutions are in essentially open tanks which allow them to evaporate, oxidize and age and become unsuitable to process film. This can only be overcome by increasing the replenishment rate or by emptying the tanks and refilling with fresh solutions. These measures are costly and time consuming. These problems are eliminated by the method and apparatus of the invention. In the method of the invention the processor can stand unused for any length of time up to the lifetime of the component solutions and then be used to produce correctly processed film.
The method and apparatus of the invention allows the processor to be small and therefore cheaper to manufacture compared with conventional large tank processors. In addition a very small area or xe2x80x9cfootprintxe2x80x9d is occupied at the processing site and thus installation is cheaper.
The method and apparatus of the invention allows an equivalent process to that run in a conventional large tank processor to have higher productivity. This is because the time required to process the entire film is equal to the total cycle time (the sum of the individual solutions times) and the film can be removed from the processor in about 4 seconds. In a conventional processor the leading end of the film exits the processor in the total cycle time but the film cannot be removed from the processor until the trailing end exits, which is several minutes later. Thus the process time equals the total cycle time plus the transport time. These restrictions are avoided by the invention.